Data Transmission Tests on Tropospheric Beyond-the-Horizon Radio System

This paper presents the results of data transmission tests made on both single-link and multi-link tropospheric beyondthe-horizon radio systems. Tests were made at 750 or 1300 bits per second employing both double sideband AM and FM methods of data modulation. In the single-link tests the data performance was determined for various transmission parameters such as median channel noise, peak channel noise, radio received carrier level, and order of diversity. Data were satisfactorily transmitted on a 2400mile circuit consisting of nine different beyond-the-horizon paths and six line-of-sight paths. The FM-type data modulation was notably superior to the AM type.